Lightly grease a 15" x 10" x 1" baking pan. Line bottom of pan with waxed/parchment paper; grease the paper. Set aside.
In a bowl, stir together, flour, cinnamon, baking powder, ginger, salt and nutmeg. Set aside.
Preheat oven to 375 degree F.
In a large mixing bowl beat eggs with an electric mixer on high speed about 5 minutes or until thick and lemon color.
Gradually add granulated sugar, beating on medium speed until light and fluffy.
With a spatula, gently stir in pumpkin and lemon juice.
Add flour mixture and keep on stirring gently until just combined.
Pour batter into the prepared pan, spreading evenly with a spatula.
Sprinkle with chopped hazelnuts.
Bake 15 minutes or until cake springs back when lightly touched.
Immediately loosen edges of cake from pan and turn cake out onto a towel sprinkled with powdered sugar. Remove paper. Cool cake completely.